Rubber compositions are often desired for tire components where one or more of uncured rubber processability and cured rubber composition properties are promoted. For example, pneumatic rubber tires are often used for purposes where traction, particularly cold weather traction, and resistance to treadwear are important considerations.
This requires tread rubber compositions which provide the desired good grip, or traction, under cold weather conditions yet also provide good rolling resistance for fuel economy and good resistance to treadwear, or abrasion resistance, for extended tire service life.
Triglycerides are main constituents of plant derived oils which are esters formed from glycerol (a trihydric alcohol containing three hydroxyl groups) and three fatty acid groups.
Algae oil (oil contained within the algae cell and recovered after cell rupture) is comprised of mixed saturated, mono-unsaturated and polyunsaturated triglyceride esters of fatty acids. Algae oil triglyderides are primarily comprised of mono-unsaturated triglyceride esters, particularly from fatty acids (fatty acid components) comprised primarily of oleic acid (e.g. 80 percent of the algae oil). It is contemplated that such triglyceride ester based algae oil might promote a combination of improved uncured rubber processing for rubber compositions containing diene-based elastomer(s) because of its high concentration of mono-unsaturation and also might promote various improved cured rubber properties in a sense of the algae oil becoming co-sulfur cured with the diene-based elastomers of the rubber composition. It is therefore desired to evaluate use of algae oil in rubber compositions containing diene-based elastomer(s) for which reinforcing filler for the rubber composition is at least one of rubber reinforcing carbon black and precipitated silica. In one embodiment, at least one of such diene-based elastomers may be a functionalized styrene/butadiene elastomer or functionalized cis 1,4-polybutadiene containing at least one functional group reactive with hydroxyl groups (e.g. silanol groups) contained on the precipitated silica reinforcing filler to aid in promoting precipitated silica reinforcement of the rubber composition.
For such evaluation, it is important to appreciate that the triglyceride ester based algae oil is chemically differentiated from petroleum (hydrocarbon) based oils, as well as from other types of plant derived oils, in a sense that the algae oil contains a significant degree of mono-unsaturation (from oleic acid) and is clearly not a linear or an aromatic petroleum based oil.
Such high oleic acid component-based triglyceride oil from algae is also chemically differentiated from more simple synthetic oleic acid based triglyceride in a sense of containing a primary oleic acid component content together with a balance of a minor content of combination of di-unsaturated and mono-unsaturated fatty acid components, particularly linoleic and palmitic fatty acids.
The chemical composition of algae oil may be determined by gas chromatographic (GC) analysis according to ASTM D5974. For the gas chromatographic analysis (GC analysis), the triglycerides of the algae are converted into fatty acid methyl esters by reflux in an acidic methanol-toluene azeotrope before the GC analysis. Gas chromatographic analysis of the fatty acid methyl esters from the algae conversion shows the high degree of mono-unsaturation and particularly a high content of tri-mono-unsaturated fatty acid component(s) of the triglyceride ester based algae oil. For informational purposes to illustrate the aforesaid relative mono-unsaturated and di-unsaturated fatty acid components for the triglyceride ester based algae oil evaluated herein and soybean oil, the following Table A is provided.
TABLE AFatty acid component of triglyceride estersAlgae OilSoybean OilOleic acid, (mono-unsaturated fatty acid)87%27%Linoleic acid, (di-unsaturated fatty acid)1.5% 38%Palmitic acid3.6% 10%Stearic acid 3% 4%
Therefore, the triglyceride based algae oil contains a very high content of mono-unsaturated oleic fatty acid component of the triglyceride esters (e.g. at least 80 percent) and minor content of di-unsaturated linoleic acid component of the triglyceride (e.g. from about 1 to about 5 percent). In contrast, the triglyceride ester based soybean oil contains a significant content of di-unsaturated linoleic acid component (e.g. at least about 30 percent). Further, such high mono-unsaturation content of the fatty acid component of the triglyceride ester based algae oil is not present in petroleum based rubber processing oil and is not seen in the triglyceride based soybean oil.
The challenge of combining such high mono-unsaturated triglyceride based algae oil for use as a rubber processing oil instead of and in contrast to petroleum based oil with diene based elastomers with reinforcing filler containing precipitated silica in an internal rubber mixer (e.g. Banbury™ mixer) is to be evaluated with results being unknown until such evaluation is undertaken.
In the description of this invention, the terms “compounded” “rubber compositions” and “compounds”, where used, refer to rubber compositions which have been compounded, or blended, with appropriate rubber compounding ingredients. The terms “rubber”, “polymer” and “elastomer” may be used interchangeably unless otherwise indicated. The amounts of materials are usually expressed in parts of material per 100 parts of rubber by weight (phr).